1. Field of the Invention
The present invention belongs to a technical field for a radio communication apparatus, and relates to an emergency notification device in the radio communication apparatus, by which a user of the radio communication apparatus notifies his position through the use of an indicator lamp therein, as well as performs essential emergency communication, when he has encountered an emergency situation such as an accident.
2. Description of the Related Art
When encountering an emergency such as a disaster, radio communication apparatus users have to voluntarily notify a lot of other radio communication apparatus users of the emergency situation.
In the case of amateur radio communication, in particular, it is recommended that a communicating frequency being in use be switched to a CALL frequency specified in each of communication frequency bands, thereby fulfilling the above-mentioned duty.
Since the frequencies of a lot of radio communication apparatuses in a call waiting state other than radio stations being in communication are set to the CALL frequency, emergency information will be widely notified. For this reason, this switching is performed.
The Japan Amateur Radio League, Inc. (JARL) designates CALL frequencies as emergency communication frequencies in VHF and UHF frequency bands for FM communication, for example. In the case of a 144 MHz frequency band, 145.00 MHz is designated as a main frequency, while 145.50 MHz is designated as a sub frequency. In the case of a 430 MHz frequency band, 433.00 MHz is designated as the main frequency, while 433.50 MHz is designated as the sub frequency.
The inventor of the present invention proposes the following radio communication apparatuses for the emergency communication:    (1) A radio-communication apparatus of U.S. Pat. No. 2,926,490, where an emergency control button is provided. In this radio communication apparatus, depression of the emergency control button when an emergency has occurred during communication at a communicating frequency or in the call waiting state causes an emergency mode to be set. Then, an emergency control code is transmitted, and automatic switching to the emergency communication frequency is also performed. On the other hand, when the emergency control code has been received, automatic transition to an emergency communication mode is performed.
In a radio communication network that uses radio communication apparatuses of this type, when a single radio communication apparatus sets the emergency mode to transmit the emergency control code, a radio communication apparatus being in communication with the radio communication apparatus or other radio communication apparatuses in the call waiting state are also switched to the emergency mode. Thus, a smooth transition to communication at the emergency communication frequency can be made in the emergency.    (2) A radio communication apparatus disclosed in Japanese Patent Unexamined Publication HEI11-8561 where an emergency mode start key is provided. In this radio communication apparatus, depression of the emergency mode start key in the case of an emergency causes a warning burst sound to be output at the maximum level from a loudspeaker. In addition, during transmission, a carrier wave of a transmitting frequency is modulated by the warning burst sound for transmission.
According to this radio communication apparatus, by superimposition of the burst sound on a received sound of the emergency communication frequency, occurrence of the emergency can be notified to radio communication users. Further, people at locations close to this radio communication apparatus, where the sound can reach, can be directly notified of the emergency by the burst sound. Accordingly, even when the owner of the radio communication apparatus cannot make a voice for help when involved in a disaster, the position of the owner can be identified by the burst sound, so that a rescue and lifesaving operation can be performed promptly.
As emergencies encountered by the owner of the radio communication apparatus, it often happens that the owner has got lost in woods at night or navigation at sea at night has become impossible.
In such emergencies, a radio communication apparatus as a method of asking for help is effective in notifying the emergencies and situations with regard to the emergencies. However, it often happens that notification of the position of the owner of the radio communication apparatus is difficult; that is, in most cases, there is no target object around the radio communication apparatus. Thus, unless the radio communication apparatus is equipped with a Global Positioning System (GPS), it is difficult for the owner to exactly clarify his position.
On contrast therewith, according to the notification unit disclosed in the invention in Japanese Patent Application HEI11-8561, which causes the burst sound to be outputted from the loudspeaker, a search operation can be performed using the sound-outputting location as the target object.
However, the volume of the sound that can be output from the radio communication apparatus is small, in general. Thus, though depending on surrounding conditions, an extent where the burst sound can reach is on the order of just several meters. In the radio communication apparatus such as a hand-held transceiver in particular, the extent becomes extremely small.
Accordingly, the radio communication apparatus may be effective as a notification unit in the case where a building fell down and was destructed due to an earthquake or the like, and the owner of the radio communication apparatus has been confined within the building. The radio communication apparatus, however, is not so effective in the case where an emergency as described above has been encountered.